“A one or two percentage point difference in alcohol content between beer brands may not sound like much, but proportionally it’s pretty big and the difference adds up over a number of drinks,” said the report’s lead scientist, William Kerr.

A federal law that requires alcohol manufacturers to list the alcohol content by volume on their products’ labels is optional for beer and wine makers, according to the San Francisco Chronicle.

U.S. federal guidelines state a standard drink has 0.6 ounces of alcohol. If a beer is 5 percent alcohol by volume, a standard drink would be 12 ounces. The article notes many European imported beers have 8 to 10 percent alcohol by volume, and several American craft beers have between 6 and 7 percent. Bud Light Platinum is 6 percent alcohol by volume.

If wine is 12 percent alcohol by volume, a standard drink would be 5 ounces. The amount of alcohol in wine varies widely, with Prosecco, Riesling and Pinot Grigio on the low end, and Petite Syrah, Madeira, Sherry and Port on the high end.

“A lot of the wines now are 14 percent or even 15 percent commonly, and the standard 5-ounce glass of wine doesn’t apply to that level,” Kerr told HealthDay. “Really a 4-ounce glass is more appropriate. And we’ve learned from our studies of bars and restaurants that the average glass is a little bit over 6 ounces.” He noted one glass of wine may actually contain about 50 percent more alcohol than a person expects.